Neanderthal demise traced in unprecedented detail

GUILTY as charged. Over the years, humans have often been accused of killing off our Neanderthal cousins, although climate change, stupidity and even bad luck have been blamed too. Now we are back in the frame.

A reassessment of major archaeological sites suggests that instead of dying out 23,000 years ago, Neanderthals were gone as early as 39,000 years ago. It also looks like we shared their territory for 5000 years, steadily replacing them as we spread across Europe.

Some say the findings support the idea that our direct ancestors pushed Neanderthals out: humans were an invasive species.

Neanderthals came to Europe some 300,000 years ago. They hunted big game with stone tools. Their territory spanned Europe and Asia. They left distinctive "Mousterian" artefacts.

What has not been clear is when and how they died out. Tom Higham of the University of Oxford and his colleagues used improved techniques to date material from 40 key sites in Europe, spanning the period when humans reached Europe and Neanderthals vanished. They studied three types of artefact. Two of them, Mousterian and Châtelperronian, are probably Neanderthal. The third kind, Uluzzian, were once attributed to late Neanderthals, but recent work suggests they were made by humans (Nature, doi.org/bxh255).

Higham and his team found that every possible or definite Neanderthal site – Mousterian and Châtelperronian – was at least 40,000 years old (Nature, DOI: 10.1038/nature13621).

"Until recently, I and many with me had thought that Neanderthals survived until 30,000 years ago, or perhaps even slightly later," says Svante Pääbo of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany. "The new dates make it clear that they disappeared 10,000 years earlier."

For Chris Stringer of the Natural History Museum in London, the findings look clear. "Neanderthals had largely, and perhaps entirely, vanished from their known range by 39,000 years ago."

Nevertheless some still believe Neanderthals lasted longer. "It is highly unlikely that all the dates are of Neanderthals about to become instantaneously extinct," says Clive Finlayson of the Gibraltar Museum.

There are Neanderthal artefacts claimed to be 23,000 years old, but Higham could not get any solid dates from them, so while a late survival is possible, there is no real evidence.

Work on material from Italy seems to show human settlers pushing Neanderthals out (see maps). Mousterian tools were common there 45,000 years ago, when human-made Uluzzian material first appeared. By 44,000 years ago, humans were sharing Italy with a dwindling Neanderthal population. By 42,000 years ago, the Neanderthals were gone.

For Pat Shipman of Penn State University, this supports her theory that modern humans acted like an invasive species in Europe, beating the Neanderthals in a competition for resources. That's a "distinct possibility", Higham says.

But that does not mean we murdered our cousins. There is no evidence humans ever killed Neanderthals, and they probably didn't meet often, says Higham.

So what role did we play? Many now suspect we were the last straw for an already fragile species. Genetics suggests Neanderthal numbers dropped sharply around 50,000 years ago. This coincides with a sudden cold snap, hinting climate struck the first blow.

By 45,000 years ago, they were probably living in small isolated groups, so were less resilient. If only one person knows how to make a certain tool, or gather medicinal plants, losing them harms the entire tribe. "The death of a few individuals might mean the death of key survival skills," says Shipman. "Neanderthals need not have been stupid or inept, just thin on the ground."

"Ultimately, there were more of us than there were of them, and we were doing similar things and hunting similar animals," says Higham. "Neanderthals became isolated and ultimately were pushed to extinction."

This article appeared in print under the headline "Decline and fall of the Neanderthals"

Correction, 1 September 2014:When this article was first published, the photograph that accompanied it was not Neanderthal, as claimed.

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